Spinal plate assembly

ABSTRACT

Spinal plate assembly, and methods of use, wherein a retaining element such as a retaining band, optionally a resiliently flexible band, mounted to a spinal plate, activates a blocking feature of the spinal plate assembly to thereby prevent the bone fastener from withdrawing out of the spinal plate assembly and past the blocking member. The apertures are typically, but not necessarily, elongate slots, elongate axes of all such slots being commonly oriented. The band can be fabricated from a variety of bio-stable, bio-compatible medical grade materials, including metals or implantable plastics. The retaining element or elements can be disposed in intermittently-located channel elements in the plate.

BACKGROUND

The present invention relates to devices for the fixation and/or supportof bones. In particular, the present invention relates to a spinal plateassembly, and a corresponding spinal plate, for the fixation and/orsupport of bones of the spinal column. The plate of the presentinvention has particular application in situations where compressionalor settling forces, as well as torsional and flexing forces, of “fixed”vertebrae on a spinal plate cause significant stressing and potentialfailure of the spinal plate and/or plate components.

Vertebral fixation has become a common approach to treating spinaldisorders and fractures, and for fusion of vertebrae at the time suchfixation is instituted. Namely, one or more vertebrae are fixed inposition relative to one or more other vertebrae above and/or below thevertebrae to be fixed. Generally, a spinal plate is the device of choiceused for mechanically supporting such vertebral fixation. A typicalspinal plate includes a plate having a plurality of aperturestherethrough. A plurality of fasteners, i.e., bone screws, are generallypositioned into and through respective ones of the apertures of theplate to secure the spinal plate to bone, such as to two or morerespective upper and lower supporting adjacent spinal vertebrae. Thescrews are fastened to the respective support vertebrae to therebyattach the spinal plate to the respective vertebrae. In general, suchplate and screw assemblies can be utilized, for example, for anteriorfixation of the spine for cervical, lumbar, and/or thoracic fixation.

The basis of anterior fixation or plating is to approach the spine froman anterior or anterio-lateral approach, and use the screws to solidlymount the spinal plate to the affected vertebrae. In addition to theapplication of a spinal plate, graft material may be combined in anattempt to permanently fuse together adjacent vertebrae. The graftmaterial can consist of bone grafts obtained from bones of the recipientor another individual.

A common problem associated with the use of such spinal plates is thetendency of the bone screws to “back out” or pull away or otherwisewithdraw from the bone into which they are mounted. This problem occurs,primarily, due to the normal torsional and bending motions of the bodyand spine. This is a particularly important problem because as thescrews become loose and pull away or withdraw from the bone, the headsof the screws can rise above the surface of the spinal plate and,possibly, even work their way completely out of the bone. While thiscondition can cause extreme discomfort for the recipient, this conditioncan also create a number of potentially serious physiological problemsgiven the significant amount of nervous and vascular structures locatedat or near the potential locations of anterior spinal plate fixations.

A number of plate assembly designs have been proposed in attempts toprevent screws from pulling away or withdrawing from the bone and/or toprevent the screws from backing out or pulling away or withdrawing fromthe surface of the spinal plate. Such mechanisms used to prevent bonescrews from pulling out of bones include cams which engage and lock thescrews, and the use of expanding head screws which expand outwardly whenadequate force is applied thereto to engage the holes in the spinalplate. All of these designs have detriments, which include potential forbreakage of the screws, or which require particular precision andalignment in their application in order to work correctly. Additionally,loose components and accessories of spinal plates, which address the“backing-out” or withdrawal problem, can get dropped and/or misplacedwhile the vertebral fixation surgical procedure is taking place,prolonging and complicating the procedure as well as creatingsubstantial risk of harm to the recipient.

Yet another common problem associated with the use of such spinal platesis the tendency, of the vertebrae which are being treated, to settleafter the spinal plate has been installed. Such settling addscompression forces to the above-listed forces, and raises theprobability that the bone screws will break, will back out, or otherwisepull away, or withdraw from the bone into which they were mounted.

It is an object of the invention to provide spinal plate assemblieswhich facilitate secure bone-to-bone fixation and/or support, such as ate.g. adjacent or second adjacent vertebrae, while accommodatingpost-procedural compression between the respective bones.

It is another object of the invention to provide spinal plate assemblieswhich afford substantial protection against pulling away or withdrawalof mounting components, which pulling away or withdrawal may result e.g.from torsional movement, flexing movement, or stress and/or dynamic loadsharing of the vertebrae, the protection thereby enhancing the bonerebuilding process carried on by the living body.

It is yet another object of the invention to provide spinal plateassemblies which attenuate application of stress on the plate apparatusand on the affixing components.

It is a further object of the invention to provide spinal plateassemblies comprising a spinal plate and resiliently movable bands, theassemblies being so mounted and positioned as to enable bone fastenersto pass such bands, with corresponding flexing or other movement of suchbands, when the bone fasteners are being installed in a recipient userand which, in combination with the designs of the bone fasteners,prevent unintended withdrawal of the bone fasteners after installationof the bone fasteners in the recipient user.

It is yet a further object of the invention to provide spinal plateassemblies which can be completely pre-assembled such that no assemblysteps need be performed on the spinal plate assembly, itself, while thespinal plate assembly is being installed in a recipient user thereof.

It is still a further object of the invention to provide spinal plateassemblies wherein apparatus, in such spinal plate assemblies, forpreventing withdrawal of bone fasteners from the bone, afterinstallation of the bone fasteners in a recipient user, areautomatically activated, to prevent such withdrawal, as a consequence ofthe installation of suitably-configured such bone fasteners.

SUMMARY

This invention provides novel spinal plate assemblies, and methods ofuse, wherein a retaining member such as a resiliently movable element,mounted to the spinal plate, as a consequence of driving a bone fastenerthrough the spinal plate assembly and into bone structure of a recipientuser of such spinal plate assembly, activates a blocking feature of thespinal plate assembly to thereby prevent the bone fastener fromwithdrawing out of the spinal plate assembly and past the resilientlymovable element.

Thus, the invention comprehends a spinal plate assembly, comprising aspinal plate, the spinal plate having a length and comprising a topsurface, a bottom surface opposite the top surface, the bottom surfacebeing adapted to be positioned adjacent bone structure of a recipientuser, and a plurality of bone-fastener-receiving apertures, theapertures being adapted to receive bone fasteners therethrough formounting the spinal plate assembly to bone structure of the recipientuser/patient; and a movable retaining element such as a movableretaining band, mounted to the spinal plate, the retaining element beingeffective, when a bone fastener is driven through an aperture into bonestructure of such recipient user, as a consequence of driving the bonefastener, to activate a blocking feature of the spinal plate assembly.The blocking feature inhibits the bone fastener from withdrawing out ofthe spinal plate assembly and past the retaining element.

In some embodiments, the retaining element is a retaining band whichextends between first and second ones of the bone-fastener-receivingapertures and extends into the first and second ones of thebone-fastener-receiving apertures.

In some embodiments, such band or other retaining element band comprisesa plastic composition which is safe for use in living human or animalbodies as an implantable plastic, and which band has suitable strength,rigidity, and deflection properties to perform the desired functions inan anticipated use environment, such as for example and withoutlimitation, one or more materials selected from the group consisting ofpolyetherimide copolymer, acetal copolymer, polyethersulfone,polyarylethersulfone, polycarbonate, ultra high molecular weightpolyethylene, polyetheretherketone, and polyaryletherketone, and blendsand mixtures of these materials.

Preferred plastic composition of the band or other retaining elementcomprises at least one of polyetheretherketone and polyaryletherketone.

In some embodiments, the retaining element comprises a resilientlymovable band, a length of the band extending alongside, and extendingacross a portion of, one or more corresponding ones of the apertures,composition and structure of the resiliently movable band being adaptedsuch that, as a bone fastener is driven alongside and past the movableband, the movable band can respond to transverse urging of the bonefastener, thereby to move transversely of the length of the band, from afirst position, until a control structure on the bone fastener is drivenpast the band, whereupon the band can return to the first position andoverlie the control structure of the so-driven bone fastener and therebyprevent the bone fastener from withdrawing.

In some embodiments, the retaining element comprises a resilientlymovable band, a length of the band extending alongside and extendingacross a portion of, one or more corresponding ones of thebone-fastener-receiving apertures.

In some embodiments, the spinal plate further comprises a channelextending downwardly from the top surface of the spinal plate, thechannel having generally opposing side walls thereof opening into andextending alongside ones of the plurality of bone-fastener-receivingapertures, the band being disposed in the channel and extending alongthe channel and into respective one or more of the apertures.

In some embodiments, at least all except two, and preferably all, of thebone-fastener-receiving apertures comprise slots, all of the slotshaving commonly oriented axes along elongate dimensions of the slots,which accommodate longitudinal movement of the bone fasteners in theslots with respect to the spinal plate after installation of the spinalplate assembly in a recipient user, thus enabling longitudinal movementof such bone fasteners in the slots, with respect to the spinal plate,after the spinal plate assembly has been installed in a recipient user.

In some embodiments, all of the bone-fastener-receiving aperturescomprise slots, having lengths greater than respective widths of theslots.

In other embodiments, first and second ones of thebone-fastener-receiving apertures comprise circular openings.

In some embodiments, all the bone-fastener-receiving apertures comprisecircular openings.

In some embodiments, the movable band extends along substantially thefull length of the spinal plate.

Preferred embodiments include a second movable band, and the first andsecond movable bands extend along substantially full lengths ofrespective first and second sides of the channel, the first and secondmovable bands collectively extending along the sides of all of thebone-fastener-receiving apertures.

In some embodiments, a second movable band has a compositioncorresponding to the composition of the first movable band, and thefirst and second movable bands collectively extend along the sides ofall of the bone-fastener-receiving apertures.

In some embodiments, the spinal plate assembly further comprises a bandretainer, optionally more than one band retainer, mounting the flexibleband or other retaining element to the spinal plate, optionally at lociaway from the bone-fastener-receiving apertures.

In preferred embodiments, the movable bands are properly positioned withrespect to the apertures so as to let control structure on the bonefastener pass below a respective movable band, with resilient movementof the movable band, and without exceeding a flexural limit of themovable band, such that the movable band returns to a blocking positionover the bone fastener after the control structure on the bone fastenerpasses below the respective movable band.

In preferred embodiments, the spinal plate is elongate, thebone-fastener-receiving apertures are arrayed in first and second rowsalong a length of the spinal plate, the spinal plate assembly furthercomprising a second resiliently flexible band, wherein the first andsecond resiliently flexible bands are mounted at the opposing side wallsof the channel, and extend along a portion of the length of the channeloccupied by the bone-fastener-receiving apertures.

In some embodiments, the retaining element comprises a resilientlyflexible band, a portion of a length of the band being positionedalongside, and extending across a portion of, one or more of theapertures.

Some embodiments of the invention include an intermittent channelextending along the length of the spinal plate, and intermittentlyexpressed adjacent the apertures, the channel optionally extendingdownwardly from the top surface of the spinal plate, optionally furthercomprising retainer structure mounting the resiliently flexible band inthe spinal plate assembly.

In preferred embodiments, the retainer structure is comprised in, and isan integral part of, the spinal plate.

In other embodiments, the retainer structure comprises one or moredistinct retainer elements.

In some embodiments, the resiliently movable band is under constantflexural stress.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pictorial view of a first embodiment of spinal plateassemblies of the invention.

FIG. 2 shows a cross-section of the spinal plate assembly of FIG. 1,taken at 2-2 of FIG. 1.

FIG. 3 shows a pictorial view of a flexible band which can be used inspinal plate assemblies of the invention.

FIG. 4 shows a pictorial view of a second embodiment of spinal plateassemblies of the invention.

FIG. 5 shows a cross-section of the spinal plate assembly of FIG. 4,taken at 5-5 of FIG. 4.

FIG. 5A is a cross-section as in FIG. 5, but at a 90 degree angle fromthe cross-section of FIG. 5, thus looking along the length of the spinalplate, and showing the resiliently flexible band flexed by passage ofthe head of a bone screw.

FIG. 5B is a cross-section as in FIG. 5A wherein the head of the bonescrew has passed the bottom of the flexible band thus to enable theresiliently flexible band to revert to its unflexed condition over thehead of the bone screw.

FIG. 6 shows a pictorial view of a third embodiment of spinal plateassemblies of the invention.

FIG. 7 shows a cross-section of the spinal plate assembly of FIG. 6,taken at 7-7 of FIG. 6.

FIG. 8 shows a pictorial view of a retainer used in the spinal plateassembly illustrated in FIG. 6.

FIG. 9 shows a pictorial view of a spinal plate used in a fourthembodiment of spinal plate assemblies of the invention.

FIG. 10 is an end view of the spinal plate illustrated in FIG. 9 withbands shown installed.

FIG. 11 shows a pictorial view of a spinal plate assembly of theinvention employing the spinal plate of FIG. 9.

FIG. 12 shows a bottom view of the spinal plate assembly of FIG. 11,illustrating the flexible bands overlapping the open aperture area ofthe bone-fastener-receiving slots.

FIG. 13 is a cross-section of the spinal plate assembly of FIG. 11,taken at 13-13 of FIG. 11.

FIG. 14 shows a bottom view of a spinal plate assembly wherein all theapertures are circular.

The invention is not limited in its application to the details ofconstruction or the arrangement of the components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments or of being practiced or carried out inother various ways. Also, it is to be understood that the terminologyand phraseology employed herein is for purpose of description andillustration and should not be regarded as limiting. Like referencenumerals are used to indicate like components.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring now to the embodiments represented by FIGS. 1-3, a spinalplate assembly 10 of the invention includes a spinal plate 12, first andsecond retaining bands or blocking members 14, and a plurality of bandretainers 16A.

Spinal plate 12 has a top surface 18, a bottom surface 20 adapted to bepositioned adjacent bone structure of a recipient user of the spinalplate assembly, and a plurality of bone-fastener-receiving apertures 22which receive bone fasteners such as bone screws 24. Apertures 22 arearranged in first and second rows of such apertures, along the length ofthe plate.

Top surface 18 of the spinal plate defines a channel 26 extending alongthe length of the support plate. As best seen in FIG. 9, channel 26 hasa bottom wall 28, opposing side walls 30, and opposing end walls 32.

Returning now to the embodiments specifically represented by FIGS. 1 and2, a given retainer 16A has a pair of opposing flanges 33, each of whichextends over one of the retaining bands 14 at a location displaced fromrespective adjacent apertures 22, whereby the respective band is trappedbetween the bottom surface 28 of the channel, the respective sidesurface of the channel, and the respective flange 33 of the retainer.Each retainer 16A includes an aperture 34. An aperture 36 in the spinalplate underlies aperture 34 in each such retainer 16A. A locking screw38 extends through aperture 34 and into aperture 36, securing retainer16A to the spinal plate. Preferably, the retainer is sized andconfigured, in combination with the side and bottom walls of thechannel, and the configurations of the bands, to apply substantial e.g.side and/or top loading pressure against the bands thereby toeffectively prevent movement of the bands with respect to the spinalplate at the location of the retainer.

Bands 14 have reduced cross-section ends 40. End walls 32 of the spinalplate include apertures 42 for receiving the reduced cross-section ends40 of the bands. Band ends 40 are accordingly received in apertures 42,thereby restraining the bands against longitudinal movement in thespinal plate assembly, as well as restraining the bands againsttransverse lateral movement at the end walls.

While bands 14 are effectively prevented from moving laterally atretainers 16A, and are prevented from moving laterally at end walls 32,as well as being prevented from moving longitudinally at end walls 32,the compositions of bands 14 can be selected such that the bandmaterial, itself, has a great degree of resilient flexural capacity.Accordingly, at locations displaced from such restraint as applied atband retainers 16A and end apertures 42, e.g. at apertures 22, the bandscan preferably readily flex in directions transverse to the lengths ofthe bands. Thus, in response to respective forces, portions of bands 14which are relatively displaced from band retainers 16A and end apertures42 can be moved along the width of plate 12, or upwardly from the plate.Such movement is, of course, limited by the restraints imposedperiodically along the lengths of the bands by band retainers 16A andend apertures 42

Side walls 30 of the channel are specifically located and configured soas to open into the sides of, and extend along and inwardly of, thesides of apertures 22.

In general, imaginary extensions of side walls 30 project acrossapertures 22 at locations displaced inwardly of the aperture side wallsby about 1 mm. Retainers 16A are so sized and configured that, when theretainers are installed, end surfaces 44 of the retainers abut the bandswith sufficient close tolerance fit that the end surfaces 44 urge thebands solidly against the side walls of the channels. Thus, bandretainers 16A position bands 14 solidly against the side walls of thechannels where the band retainers interface with the bands, andtypically not where the bands are passing over apertures 22. With thebands solidly against the side walls of the channel, theoutwardly-disposed sides 46 of the bands are in surface-to-surfacecontact with side walls 30 of the channels. The outwardly-disposed sides46 of the bands, the respective rows of apertures 22, and retainers 16A,are thus correspondingly cooperatively sized, arranged and configuredwith respect to each other such that, when bands 14 are trapped betweenthe channel side walls, the channel bottom, and the retainers, thebands, when not deflected by the bone screws, extend along a pathwherein the outwardly-disposed sides 46 of the bands extend closelybeside the side walls 30 of the channel. Since imaginary extensions ofthe side walls are displaced inwardly, into the apertures, of theaperture side walls by about 1 mm, the outwardly-disposed side walls ofthe bands also are displaced inwardly, into the apertures, of theaperture side walls by about 1 mm.

FIGS. 4 and 5 illustrate a second family of embodiments of theinvention. In these embodiments, all elements of the invention are thesame as in the embodiments of FIGS. 1 and 2, except for the retainer andits interactions. While retainer 16A in FIGS. 1 and 2 is held in placewith a locking screw 38, and has flanges 33 interfacing with the tops ofbands 14, in the embodiments of FIGS. 4 and 5, retainers 16B aredisposed in abutting relationship with bands 14, and are spot welded atwelds 48 to bands 14. Further, retainers 16B preferably, but notnecessarily, have studs (not shown in FIGS. 4-5) which extend throughrespective apertures corresponding to apertures 36 in plate 12 of FIGS.1 and 2. Studs (not shown in FIGS. 4-5) can extend through the plateapertures and can be spot welded to the plate at the bottom wall of theplate. Such apertures, studs, and spot welds are shown in e.g. FIGS. 6and 7, discussed following.

Thus, the retainers of FIGS. 4 and 5 interact with the bands through theabutment interface in combination with the spot welds between the bandsand the retainers, and use the abutment interface, in combination withclose fit tolerances, to urge the bands into frictional engagement withthe side walls of the channel, and do not extend over the bands,themselves.

FIGS. 5, 5A, and 5B illustrate the process by which a band 14 is flexedor is otherwise caused to move when a bone screw 24 passes the band, andfurther illustrate the interference in a withdrawal path of the screw,provided by the band after the screw has been driven past the band andthe band has returned to the less flexed or unflexed condition.

Turning especially to FIG. 5A, bone screw 24 has a head 56 and a shank58. Head 56 has a tapered, or beveled, or conical lower surface 60, anda generally flat or concave upper surface 62 adjacent the outer edge 64of the head. By generally flat upper surface is meant that the uppersurface is generally perpendicular to a central longitudinal axis ofshank 58.

As screw 24 is installed by turning the screw and thus advancing thescrew into bone tissue of the recipient, and through one of the bonescrew apertures, the angled lower surface 60 of the screw headapproaches and pushes against band 14 at the top inner edge 66 of theband. As lower surface 60 is progressively advanced downwardly as aconsequence of advancing the screw into the bone, and against band 14,the tapered angle of the lower surface of the head of the bone screwapplies a transverse, side-loading force on band 14, urging the band tomove away from the longitudinal axis of shank 58. As illustrated in FIG.5A, the band can move at the locus of engagement with the lower surfaceof the screw head, thus to enable further driving of the screw, andfurther temporary displacement of the band, by continuing downwardmovement of the screw head. As soon as the top outer edge 64 of the headpasses below band 14, the band moves back over head 56 as shown in FIG.5B. Thus, the band serves as a safety device preventing withdrawal ofthe bone screw from the bone, and from the spinal plate assembly.

FIGS. 6-8 illustrate a third family of embodiments of the invention. Inthe embodiments of FIGS. 6-8, all elements of the invention are the sameas in the embodiments of FIGS. 1-5, except for the retainer and itsinteractions. Retainer 16A in FIGS. 1 and 2 has a flange 33 whichoverlies bands 14, and is secured to plate 12 with a locking screw 38.Retainer 16B in FIGS. 4 and 5 interacts with bands 14 by abutment,fortified by spot welds to bands 14, and is secured to plate 12 withspot welds. In the family of embodiments represented by FIGS. 6-8,retainer 16C has flanges 33 (best illustrated in FIG. 8) which overliebands 14 as in FIGS. 1 and 2 and has a stud 50 extending throughaperture 36 in plate 12, as discussed with respect to FIGS. 4 and 5.Stud 36 is spot welded to plate 12 by welds 52 at bottom surface 20 ofthe plate. Accordingly, the securement to the plate is by spot weldsdisplaced from apertures 22 and from bands 14. Interaction between bands14 and retainer 16C is through overlying flanges 33 of the retainer,whereby the bands are not subjected to the direct thermal affects of thespot welding process.

FIGS. 9-13 illustrate a fourth family of embodiments of the invention.In the embodiments of FIGS. 9-13, all elements of the invention are thesame as in the previous embodiments except for the retainer and itsinteractions, and the length and number of apertures, and correspondinglength of plate 12. As seen therein, the plate in FIGS. 9-13 has only 3bone screw receiving apertures 22 in each of the two rows of apertures.Retainer 16D, like retainer 16C has flanges 33 which overlie the bands.However flanges 33, seen especially in FIGS. 11 and 13, of retainers 16Dhave generally round configurations, and extend generally the fulllength of a portion of the channel side wall between respective ones ofthe apertures 22, while having straight-line edges at the side walls.Such increased flange footprint provides, in flange 33 of e.g. FIG. 11,controlling interaction over an increased fraction of the length of thebands between apertures 22, as compared to the previous embodiments,whereby control of transverse movement of the bands is extended tosubstantially the full length of that portion of the side wall whichextends between adjacent ones of apertures 24. Retainer 16D has a stud50 which extends through an aperture 36 in the plate and is spot-weldedat welds 52.

FIG. 10 illustrates the reduced cross-section ends 40 of bands 14 in endapertures 42, wherein the relatively larger cross-section main bodies ofthe bands are restrained against longitudinal movement by interactionwith the inner surfaces of end walls 32.

FIG. 12 illustrates a bottom view of assembly 10, directly illustratingthe interference path set up by bands 14, to interfere with properlyfitting bone screws, adjacent the inner edges of apertures 22. Asindicated above, a preferred interference dimension “I”, between theside of the aperture and the edge of the respective band, isapproximately 1 mm. Such interference dimension can, of course, bedifferent, depending on a variety of parameters relating to the specificstructural and operating environments, including the relativeconfigurations of the bone screw, the aperture, and the band. What isimportant is that the interference be of sufficient dimension, and thatthe interfering surfaces be so cooperatively configured, that the bandeffectively interferes with the bone screw so as to prevent the bonescrew from withdrawing from assembly 12 without intentional provisionfor such withdrawal.

Thus, in the illustrated embodiments, the angle at which lower surface60 of the screw head interacts with band 14 as the bone screw is beingdriven through plate 12 is effective to move the band sideways, out ofthe way of the head whereby the head can pass beyond the band.Correspondingly, the upper surface 62 of the head is so configured as tonot automatically move band 14 sideways if and as the bone screw beginsto back out of engagement with the bone and the plate. Rather, as thescrew begins to back out, the upper surface 62 of the head comes intoabutting relationship with the band, whereby band 14 serves as anautomatic and effective stop, preventing the screw from backing out ofthe underlying bone into which the screw is screwed. Band 14 thus servesas a safety device, preventing inadvertent withdrawal of screw 24, whileenabling facile installation of the screw.

FIG. 14 illustrates a bottom view of a fifth family of embodiments ofassembly 10 wherein all of apertures 22 are circular. Such support plateassemblies have limited or no freedom of movement of the bone screwswith respect to the plate, whereby the spinal plate assembly restrainsmovement of the bone structure to which the spinal plate assembly ismounted. Such support plate assemblies are desirable where the bonepositions may be desirably fixed, and are not expected, or not desired,to move with respect to each other.

Since spinal plate assemblies of the invention are to be used withinliving bodies, all materials used in the spinal plate assemblies must becompatible with, and safe for use inside, the living body, e.g. animalbodies or the human body. In that regard, preferred material for spinalplate 12, and retainers 16A is titanium, or titanium alloy, for exampletitanium-aluminum alloy. A specific titanium aluminum alloy referred toin ASTM F-136 is (Ti6AL-4V).

Plate 12 has a length sufficiently long to span at least two vertebrae,and width and thickness sufficiently great to provide resistance tobending and torsion forces. Accordingly, where plate 12 is composed ofone of the above referred to materials, typical dimensions are asfollows. Typical length is at least 20 mm, up to as great as about 120or more mm. Width is typically about 15 mm to about 20 mm. Nominalthickness is typically about 2 mm to about 3.5 mm. The bottom of channel26 is typically about 0.7 mm to about 1.5 mm from the top surface of theplate. Such dimensions are, of course, exemplary only and not limitingand, given the above exemplary dimensions, those skilled in the art canvary such dimensions according to specific structure of respectiveplates and plate assemblies.

Compositions for bands 14 preferably have resilient, e.g. spring-like,flexural properties. Resilient flexural capability can be propertiesinherent in the metal composition, or can be properties which attend thecross-sectional structure designed into the width and thickness of therespective band, in combination with the metal composition. For example,materials which are not generally considered as having resilient,spring-like properties can, when fabricated into sufficiently smallcross-sections, perform the desired resiliently flexural springfunction. For example and without limitation, bands 14 can employtitanium compositions, titanium alloy compositions such astitanium-aluminum alloy compositions, for example the specific titaniumaluminum alloy mentioned above, or other titanium alloys, or stainlesssteel compositions which, in sufficiently small cross-section, canexhibit the desired resilient spring-like properties. Other materialscan be used as bands 36 and retainers 16 so long as such materialssatisfy the above safety and performance requirements. All materialsused in the plate assembly are, of course, medical grade materials.

Any of the plastic materials known to be safe for use in living human oranimal bodies, as applies, as implantable plastics, and which havesuitable hardness and rigidity, can be employed for fabricating bands36. As with the metals, such materials must be both bio-stable andbio-compatible.

As such plastics, there can be mentioned, for example and withoutlimitation, polyetherimide copolymer such as ULTEM®, acetal copolymer,

-   -   polyethersulfone, also known as polyarylsulfone, such as RADEL        A®,    -   polyarylethersulfone such as RADEL R®,    -   polycarbonate,    -   ultra high molecular weight polyethylene,    -   polyetheretherketone, also known as PEEK, available from        Boedecker Plastics, Inc. Shiner, Tex.,    -   polyaryletherketone, also known as PEEK-OPTIMA@.

Such materials can be filled or unfilled, and can employ the usualadditives, including processing aids, so long as the resultantcomposition is suitable as an implantable plastic for use in a living,e.g. human, body.

The spinal plates illustrated herein have closed-end channels 26 whichare closed at end walls 32, with apertures 42 extending through the endwalls of the channels. The invention also contemplates spinal plateswherein the channels extend the entire lengths of the plates, and arethus open ended channels (not shown). Where open ended channels areused, end retainers (not shown) can be employed to close off the ends ofthe channels. Such end retainers include end apertures corresponding toapertures 42, whereupon the combination of the open channel and theclosing end retainers result in the same, or very similar, channelcross-section configuration at the ends of plate 12.

Channel 26 has a width sized so that the side walls extend intoapertures 22 a distance sufficient to generate an interference betweenbands 14 and apertures 22 when the bands are disposed against side walls30 and are in relatively less-flexed, or unflexed conditions. Channel 26has a depth sufficient to accommodate the thicknesses of bands 14.

In a family of embodiments (not shown), channel 26 can be intermittent,and exist only adjacent apertures 22. In such embodiments, bands 14 areheld in channel elements which extend e.g. downwardly from top surface18 of plate 12, and which thus define the band paths. Separate retainers16 are not needed, and the functions of the retainers can be provided byplate material at or adjacent the respective intermittent expressions ofchannel 26.

As a result of the structures of apertures 22, channel side walls 30,retainers 16A, 16B, 16C, or 16D, and bands 14, when a bone screw, whichproperly fits the apertures 22, is driven through an aperture 22, thehead of the bone screw pushes against the respective band 14 as shown inFIG. 5A, and forces the band in a width-wise transverse direction awayfrom the aperture in order that the head of the bone screw can pass theband. Since the band is preferably readily and resiliently flexible, theband flexes in response to the urging of the head of the bone screw, asshown in FIG. 5A. When the head of the bone screw passes below thebottom of the band, the band is no longer being held in the flexedcondition by the screw head, and resiliently returns to the previouscondition of being unflexed, thereby setting up a potentialinterference, of about 1 mm, between the band and the screw head, whichinterference is activated if and when the screw begins to back out of,or withdraw from, the bone plate.

The invention contemplates that bands 14 can be arranged in other than arest, or straight, condition when not being forced sideways by the screwhead. Thus, the bands can be under a degree of constant flexural stress,e.g. a pre-stressed condition, wherein the level of stress is changed asthe head of the screw passes, and then reverts to the previous level ofstress after the screw head passes.

Similarly, bands 14 can be in a non-straight, e.g. curvilinear orangled, configuration in a rest condition, and can still resilientlyflex with respect to the bone screw as the bone screw is driven past theband.

If desired, some control structure other than the head of the screw canbe used to activate and release the band. For example, control structure(not shown) can be designed into the screw below the head, above thehead, or otherwise, for the purpose of activating the flexural andrelease properties of the band.

Whatever the positions of the band, whatever the control structure onthe screw which interfaces with the band, once the band is released fromthe flexing of the respective control surface of the screw, and the bandthus returns to the pre-stress flex condition, the band is positionedabove, over, and in an interfering abutment position with respect to apath which some portion of the screw must traverse in order to withdrawfrom the spinal plate assembly. Referring to FIGS. 5 and 5B wherein thehead of the screw has passed below the bottom of the band, and whereinthe band has thus returned to the pre-stressed condition, the band isseen to overlie a portion of the surface of the head of the screw, suchthat if the screw begins to withdraw e.g. away from the plate, the headof the screw impacts the bottom of the band. As withdrawal of the screwprogresses such that the screw impacts the bottom of the band, the band,being supported by respective retainers 16A, 16B, 16C, or 16D, preventsthe screw from further withdrawal from the plate.

As seen in FIG. 5A, when the screw is driven through the plate, e.g. andinto bone material of a recipient user of the spinal plate assembly, theforce applied by the upwardly-extending angular bottom surface of thescrew automatically pushes the band aside as the head of the screwimpacts and passes the band. Once the head of the screw passes the band,the band automatically resiliently restores itself to the unflexed orless-flexed position over the head of the screw, illustrated in FIGS. 5and 5B. Thus, in spinal plate assemblies of the invention, driving thebone screw, and thereby mounting the spinal plate assembly in the bodyof a recipient user thereof, automatically flexes the band, as ablocking member, out of the way of insertion of the bone screw, and thenthe blocking member/band automatically flexes to a locking, blockingposition over the head or other control structure of the screw, therebyautomatically activating the blocking and locking feature of the spinalplate assembly to block withdrawal of the bone screw, and thus to lockthe bone screw in the assembly and retain joinder of the bone screw tothe respective bone of the recipient user. Such bone screw can, ofcourse be released for removal by manually or otherwise intentionallyflexing the band away from the screw, and removing the screw while theband is thus held in the moved or flexed condition.

In preferred embodiments of the invention, all of apertures 22 areslot-shaped in that, e.g. in projection, each aperture has an elongatedimension and a shorter cross-dimension. In some embodiments, two of theapertures are relatively lesser lengths, and may be e.g. circular,thereby to serve as support apertures, and the remaining apertures arerelatively greater lengths, as slots or slot-shaped, and serve as settleapertures, providing for the bone structure to settle while being heldby the spinal plate. As seen in FIGS. 1 and 2, typically each aperturealong the length of the spinal plate assembly is progressivelylonger/shorter, in a progressive pattern, than the adjacent apertures inthe same row to accommodate the typically progressively increasingdistance moved by respectively more upwardly-disposed ones of thevertebrae being treated by the plate assembly.

Typical length increments for adjacent apertures in a given row areabout 1 mm. Accordingly, in a plate 12 as in FIG. 11, having threeapertures per row, the length differential between the longest andshortest apertures 22 can be, for example, about 2 mm. Correspondingly,in a plate 12 as in FIG. 1 having six apertures per row, the lengthdifferential between the longest and shortest apertures 22 can be, forexample, about 5 mm. The exact and actual length differentials can besomewhat different, depending on the specific use contemplated for therespective plate 12.

Typically, spinal plate assemblies of the invention have two rows ofapertures. And while the spinal plate assemblies illustrated in thedrawings show 2 rows of bone screw apertures, the invention can well beutilized with any number of rows of apertures, and any number ofapertures per row.

Further to other embodiments, bands 14 are shown with each bandextending the full length of channel 26. It is contemplated that bands14 can be segmented so as to comprehend 2 or more bands extending e.g.serially along one or both of side walls 30. For example, a separateband can be used in support of the function of each or any aperture.

While plates 12 are shown having apertures 22 arrayed along the fulllength of the plate, the using surgeon selects the particular aperturesthrough which bone screws can suitably be employed to mount the plate tobone structure of the recipient user. The particular apertures employeddepend on the needs presented by the surgery being performed. Thus, bonescrews can be employed through any number, at least 2, and up to all, ofthe apertures.

Where an aperture is a slot-shaped aperture, a bone screw employedthrough that aperture is advanced a sufficient distance to bring thecontrol structure of the screw past the respective band, but not asufficient distance to force the head of the screw against a side wallof the aperture, such as by a friction lock. With the screw head thusunsecured to the aperture walls, the screw is free to move with respectto the plate as the bones, into which the screws have been inserted,move and settle with respect to each other.

Where slot-shaped apertures are used to enable post-procedure movementof the bone screws to accommodate post-procedure settling of vertebraein a recipient user, all of such apertures which are to participate insuch settling are arranged with common orientation of the axis of theelongate dimensions of the apertures so as to reduce the possibilitythat any of the bone screws might frictionally bind against a side wallof the aperture while in the process of moving so as to accommodate suchsettling. Namely, the bone screws do not, cannot, frictionally bind inthe slot-shaped apertures, as such binding would obviate any objectiveof accommodating sliding of the bone screws in apertures 22.

Where apertures 22 are round, whereby no sliding of the bone screws iscontemplated, the screw heads can be frictionally bound to plate 22 ifdesired.

Those skilled in the art will now see that certain modifications can bemade to the apparatus and methods herein disclosed with respect to theillustrated embodiments, without departing from the spirit of theinstant invention. And while the invention has been described above withrespect to the preferred embodiments, it will be understood that theinvention is adapted to numerous rearrangements, modifications, andalterations, and all such arrangements, modifications, and alterationsare intended to be within the scope of the appended claims.

To the extent the following claims use means plus function language, itis not meant to include there, or in the instant specification, anythingnot structurally equivalent to what is shown in the embodimentsdisclosed in the specification.

1. A spinal plate assembly, comprising: (a) a spinal plate, said spinalplate having a length and comprising a top surface, a bottom surfaceopposite the top surface, and a plurality of bone-fastener-receivingapertures; and (b) a first transversely movable retaining elementmounted to said spinal plate, and extending from a first said one ofsaid bone-fastener-receiving apertures, along the length of said spinalplate to a second one of said bone-fastener-receiving apertures, andextending into at least one of said bone-fastener-receiving apertures;and (c) a second transversely movable retaining element mounted to saidspinal plate, and extending from a third one of saidbone-fastener-receiving apertures, along the length of said spinal plateto a fourth one of said bone-fastener-receiving apertures, and extendinginto at least one of said bone-fastener-receiving apertures. 2-6.(canceled)
 7. A spinal plate assembly as in claim 1 wherein compositionof said spinal plate comprises at least one of titanium and titaniumalloy.
 8. A spinal plate assembly as in claim 1 wherein composition ofsaid first and second retaining elements comprises at least one oftitanium, titanium alloy, and stainless steel. 9-10. (canceled)
 11. Aspinal plate assembly as in claim 1, said first and second retainingelements comprise a resiliently flexible bands, lengths of said bandsextending alongside and extending across portions of one or morecorresponding ones of the bone-fastener-receiving apertures.
 12. Aspinal plate assembly as in claim 1, said spinal plate furthercomprising a channel extending downwardly from the top surface of saidspinal plate, the channel having opposing side walls thereof openinginto and extending alongside ones of said plurality ofbone-fastener-receiving apertures, said retaining elements beingdisposed in said channel and extending along the channel.
 13. A spinalplate assembly as in claim 2, said spinal plate further comprising achannel extending downwardly from the top surface of said spinal plate,the channel having opposing side walls thereof opening into andextending alongside ones of said plurality of bone-fastener-receivingapertures, said retaining elements being disposed in said channel andextending along the channel. 14-17. (canceled)
 18. A spinal plateassembly as in claim 1 wherein said retaining elements extend alongsubstantially the full length of said spinal plate. 19-20. (canceled)21. A spinal plate assembly as in claim 3, said retaining elementscomprising a movable retaining bands, and further comprising a bandretainer securing said bands to said spinal plate while accommodatinglimited movement of said bands while said bands are is secured to saidspinal plate. 22-26. (canceled)
 27. A spinal plate assembly as in claim1, said retaining elements comprising resiliently flexible bands,portions of lengths of said band being positioned alongside, andextending across portions a portion of one or more of the apertures. 28.A spinal plate assembly as in claim 27, including an intermittentchannel (26) extending along the length of the spinal plate, andintermittently expressed adjacent the apertures.
 29. A spinal plateassembly as in claim 1, said retaining elements comprising a resilientlyflexible bands, portions of lengths of said bands extending across atleast one of the apertures, said spinal plate further comprising anintermittent channel (26) extending along the length of said the spinalplate, and intermittently expressed adjacent the apertures, and whereinthe compositions of said retaining elements comprise at least one oftitanium, titanium alloy, and stainless steel.
 30. A spinal plateassembly as in claim 27, the channel extending downwardly from the topsurface of said spinal plate.
 31. A spinal plate assembly as in claim29, the channel extending downwardly from the top surface of said spinalplate.
 32. A spinal plate assembly as in claim 27, further comprisingband retainer structure securing said resiliently flexible bands in saidspinal plate assembly.
 33. (canceled)
 34. A spinal plate assembly as inclaim 32 wherein said band retainer structure is comprised in, and is anintegral part of, said spinal plate. 35-39. (canceled)
 40. A spinalplate assembly as in claim 3 wherein at least all except two of saidbone-fastener-receiving apertures comprise slots, having commonlyoriented elongate axes enabling longitudinal movement of bone fastenersin said slots, with respect to said spinal plate after the spinal plateassembly is installed in a recipient user of said spinal plate assembly.41. A spinal plate assembly, comprising: (a) a spinal plate, said spinalplate having a length and comprising a top surface, a bottom surfaceopposite the top surface, the bottom surface being suitable for beingpositioned adjacent bone structure of a recipient user, and a pluralityof bone-fastener-receiving apertures, said spinal plate furthercomprising an intermittent channel (26) extending along the length ofthe spinal plate, and intermittently expressed adjacent the apertures;and (b) a retaining band mounted to said spinal plate, said retainingband being effective, when a bone fastener is driven through a saidaperture into bone structure of a recipient user, and past saidretaining band, as a consequence of driving such bone fastener, toactivate a blocking feature of said spinal plate assembly, whichblocking feature inhibits the bone fastener withdrawing out of saidspinal plate assembly and past said retaining band.
 42. A spinal plateassembly as in claim 41 wherein the channel intermittently extends fromthe top surface of said spinal plate toward the bottom surface of saidspinal plate, the channel having a side wall opening into a respectiveone of said plurality of bone-fastener-receiving apertures, said bandcomprising one or more bands disposed in the channel.
 43. A spinal plateassembly as in claim 42, further comprising band retainer structuremounting the retaining band in said spinal plate assembly. 44-48.(canceled)